MyBatis的高级查询与映射

1，导入MyBatis的依赖

<dependencies>

            <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
            <dependency>
                <groupId>org.mybatis</groupId>
                <artifactId>mybatis</artifactId>
                <version>3.4.6</version>
            </dependency>

            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.46</version>
                <scope>runtime</scope>
            </dependency>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.12</version>
                <scope>test</scope>
            </dependency>
        </dependencies>

2，需要映射的实体类，User.class,Order.class

public class User {
    private  int id;
    private String username;
    private String password;
    private String email;
    private String gender;
    private int flag;
    private int role;
    private String code;

    private List<Order> orders;


    public List<Order> getOrders() {
        return orders;
    }

    public void setOrders(List<Order> orders) {
        this.orders = orders;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public int getFlag() {
        return flag;
    }

    public void setFlag(int flag) {
        this.flag = flag;
    }

    public int getRole() {
        return role;
    }

    public void setRole(int role) {
        this.role = role;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }


    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", email='" + email + '\'' +
                ", gender='" + gender + '\'' +
                ", flag=" + flag +
                ", role=" + role +
                ", code='" + code + '\'' +
                ", orders=" + orders +
                '}';
    }
}

public class Order {
    private  String id;
    private  int money;

    private String status;


    private List<Orderdetail> orderdetailList;

    public List<Orderdetail> getOrderdetailList() {
        return orderdetailList;
    }

    public void setOrderdetailList(List<Orderdetail> orderdetailList) {
        this.orderdetailList = orderdetailList;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public int getMoney() {
        return money;
    }

    public void setMoney(int money) {
        this.money = money;
    }

    @Override
    public String toString() {
        return "Order{" +
                "id='" + id + '\'' +
                ", money=" + money +
                ", status='" + status + '\'' +
                ", orderdetailList=" + orderdetailList +
                '}';
    }

}

3，MyBatis的接口mapper类UserMapper.class

/**
 * Created by davidshion 2/9/20/6:27 PM
 * 相当于以前的dao接口
 *
 * @Author davidshi
 */
public interface UserMapper {
     User findUserById(int id);

     List<User> findUserByMult(User user);
     List<User> findUserByMult1(User user);

     List<User> findUserByIds(List<Integer> ids);
     List<User> findUserByIds1(QueryVo queryVo);

     User findUserAndOrderByUserId(int id);

     User findUserAndOrderAndOrderDetailByUserId(int id);
}

4，Mapper的具体实现UserMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<!--这个地方必须是对应的接口的权限定名称-->
<mapper namespace="person.david.mybatis.mapper.UserMapper">
    <!--
    id必须和接口中对应方法的名字一样
    parameterType 必须和方法的参数一致
    resultType必须和方法的返回值一致
    -->
    <select id="findUserById" parameterType="int" resultType="person.david.mybatis.pojo.User">
        select * from tb_user where  id =#{id}
    </select>


    <!--<insert id="insertUser" parameterType="person.david.mybatis.pojo.User">-->
        <!--INSERT INTO tb_user (username,password,email,gender,flag,role,code) VALUES (#{username},#{password},#{email},#{gender},#{flag},#{role},#{code})-->

    <!--</insert>-->
    <!---->
    <!---->
    <!--<select id="findUserByNameAndGender" parameterType="person.david.mybatis.pojo.User" resultType="person.david.mybatis.pojo.User">-->
        <!--select * from tb_user where username like '%${username}%' and  gender=#{gender}-->
    <!--</select>-->

    <!--<select id="findUserByNameAndGender1" parameterType="person.david.mybatis.vo.QueryVo" resultType="person.david.mybatis.pojo.User">-->
       <!---->
        <!--select * from tb_user where username like '%${user.username}%' and  gender=#{gender} limit(#{pianyi},10)-->
        <!---->
    <!--</select>-->


    <!--查询数据的时候,会有多个条件
        但是这些条件会出现可能会有,可能没有的情况
    select * from xxx where a=xxx and b =xxx and c =xxx

    不允许出现where 1=1 因为这会导致数据库索引失效
      <where> 会自动去掉第一个符合条件的and
    -->
<!--

声明一个sql语句,此语句可以被复用 使用方式在使用的地方通过include id= sql id
-->
    <sql id="getall">
        SELECT  id, username, password, email, gender, flag, role, code from tb_user

    </sql>


<select id="findUserByMult" resultType="person.david.mybatis.pojo.User">


    SELECT  id, username, password, email, gender, flag, role, code from tb_user

  <where>
    <if test="username!=null and username !=''">

        and username=#{username}

    </if>

    <if test="email!=null and email !=''">

        and email=#{email}

    </if>
  </where>
</select>

<!--
include
导入一条已经声明好的sql语句
-->
    <select id="findUserByMult1" resultType="person.david.mybatis.pojo.User">
        <include refid="getall"/>
        <where>
            <if test="username!=null and username !=''">
                and username=#{username}
            </if>
            <if test="email!=null and email !=''">
                and email=#{email}
            </if>
        </where>
    </select>

<!--
两个问题, 集合如何获取
集合如何遍历
collection 代表要遍历的存放参数的集合
item 每次遍历后的参数存放的位置
open 遍历之前添加什么内容
close 遍历完成之后添加什么
separator 分隔符 ,每次遍历之后添加分隔符,但是最后一次遍历不添加
-->
    <select id="findUserByIds" parameterType="arraylist" resultType="person.david.mybatis.pojo.User">
        select * from tb_user
      <where>
          <if test="list !=null">
            <foreach collection="list" item="id" open="id in (" close=")" separator=",">
                #{id}
            </foreach>
          </if>
      </where>
    </select>


    <select id="findUserByIds1" parameterType="person.david.mybatis.vo.QueryVo" resultType="person.david.mybatis.pojo.User">

        select * from tb_user
        <where>
            <if test="ids !=null">
                <foreach collection="ids" item="id" open="id in (" close=")" separator=",">
                    #{id}
                </foreach>
            </if>
        </where>

    </select>

    <resultMap id="basemap" type="person.david.mybatis.pojo.User">

        <id column="uid" property="id"></id>
        <result column="username" property="username"/>
        <result column="password" property="password"/>
    </resultMap>


<!--
一对多的关系
collection 在user对象中 oders集合的属性名, 也就多的一方在少的一方中的属性名
ofType 集合的泛型
-->

    <resultMap id="userorderresultmap" type="person.david.mybatis.pojo.User" extends="basemap">
        <!--<id column="uid" property="id"></id>-->
        <!--<result column="username" property="username"/>-->
        <!--<result column="password" property="password"/>-->

            <collection property="orders" ofType="person.david.mybatis.pojo.Order">
                <id column="id" property="id"></id>
                <result  column="money" property="money"/>
                <result column="status" property="status"/>
            </collection>
    </resultMap>


    <select id="findUserAndOrderByUserId" resultMap="userorderresultmap">
        select  u.id uid , u.username, u.password,o.id,o.money,o.status from tb_user u ,tb_order o where  u.id=o.uid and u.id =#{id}

    </select>





    <resultMap id="userorderdetailresultmap" type="person.david.mybatis.pojo.User" extends="basemap">
        <!--<id column="uid" property="id"></id>-->
        <!--<result column="username" property="username"/>-->
        <!--<result column="password" property="password"/>-->

        <collection property="orders" ofType="person.david.mybatis.pojo.Order">
            <id column="id" property="id"></id>
            <result  column="money" property="money"/>
            <result column="status" property="status"/>

            <collection property="orderdetailList" ofType="person.david.mybatis.pojo.Orderdetail">
                <id column="odid" property="id"></id>
                <result column="num" property="num"></result>
                <result column="money" property="money"></result>
            </collection>

        </collection>

    </resultMap>


    <select id="findUserAndOrderAndOrderDetailByUserId" resultMap="userorderdetailresultmap">
        select  u.id uid , u.username, u.password,o.id,o.money,o.status ,od.id odid, od.num,od.money from tb_user u ,tb_order o ,tb_orderdetail od where  u.id=o.uid and o.id=od.Oid and u.id =#{id}

    </select>
</mapper>

5，MyBatis的配置类SqlMapConfig.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <settings>
        <!-- 打印查询语句 -->
        <setting name="logImpl" value="STDOUT_LOGGING" />
    </settings>
   <!--配置和数据库链接相关的信息-->
    <!--四大件
    驱动
    地址
    用户名
    密码
    default 默认的环境, 在这个配置文件中 可以创建多个环境,如果有多个的时候需要指定默认值,这个值就是下面环境的id值
    -->
    <environments default="abc">

        <environment id="abc">
            <!--
            固定值JDBC
            -->
            <transactionManager type="JDBC"></transactionManager>

            <!--数据源 其实就是一个连接池
            可以使用mybatis默认的连接池POOLED
            -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql:///db_shopping?useUnicode=true&amp;characterEncoding=UTF8"/>
                <property name="username" value="root"/>
                <property name="password" value="qishimeiyoumima"/>
            </dataSource>
        </environment>

    </environments>

 <mappers>

     <!--<mapper resource="com/qianfeng/mybatis/mapper/UserMapper.xml"/>-->
     <!--<mapper resource="com/qianfeng/mybatis/mapper/UserMapper.xml"/>-->
        <!--<mapper class="person.david.mybatis.mapper.OderMapper"/>-->
     <!--扫描指定包下面的所有的xml文件
     注意,扫包,什么功能所在的文件在什么位置,你要扫描到具体的位置
     -->
        <package name="person.david.mybatis.mapper"/>

 </mappers>

</configuration>

6，测试类TestMain.class

public class TestMain {
    private SqlSessionFactory sqlSessionFactory;

    @Before
    public void before() throws IOException {
        InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
    }

    @Test
    public void test1() {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);//通过动态代理的方式获取到Usermapper的一个代理对象
        User user = userMapper.findUserById(10);//执行流程 1.当你调用这个方法的时候,因为是一个动态代理对象,所以mubatis内部会拦截你调用的方法,然后可以获取到方法的权限定名称,而这个名称其实就是mapper中你要执行的sql的唯一标记,参考我们普通的编写方式,2 在内部又转换成我们原始的调用方式
        System.out.println(user);
        // "com.qianfeng.mybatis.mapper.UserMapper.findUserById"
        //反射只提供最基本的操作,就相当于我们盖楼的时候基础部件,比如砖,水泥,钢筋
        //

        sqlSession.close();
    }

    @Test
    public void test2() {
        StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();
        String methodName = stackTrace[1].getMethodName();
        String name = this.getClass().getName();
        System.out.println(name);
        System.out.println(methodName);
    }

    @Test
    public void test3(){
        User user = new User();
        user.setUsername("王三十");
        //user.setEmail("wangsanshi1.com");

        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> result = mapper.findUserByMult(user);
        System.out.println(result);
    }

    @Test
    public void test4(){
        User user = new User();
        user.setUsername("王三十");
        //user.setEmail("wangsanshi1.com");

        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> result = mapper.findUserByMult1(user);
        System.out.println(result);
    }


    @Test
    public void test5(){
        List list = new ArrayList();
        list.add(2);
        list.add(3);
        list.add(4);
        list.add(5);
        list.add(6);
        list.add(7);
        list.add(8);
        list.add(9);
        list.add(10);
        list.add(11);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> result = mapper.findUserByIds(list);
        System.out.println(result);
    }

    @Test
    public void test6(){
        QueryVo queryVo = new QueryVo();
        List list = new ArrayList();
        list.add(2);
        list.add(3);
        list.add(4);
        list.add(5);
        list.add(6);
        list.add(7);
        list.add(8);
        list.add(9);
        list.add(10);
        list.add(11);
        queryVo.setIds(list);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> result = mapper.findUserByIds1(queryVo);
        System.out.println(result);
    }

    @Test
    public void test7() {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.findUserAndOrderByUserId(9);
        System.err.println(user+"========>"+user.getOrders().size());
    }

    @Test
    public void test8() {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.findUserAndOrderAndOrderDetailByUserId(9);
        System.err.println(user+"========>"+user.getOrders().size());
    }
}